The present invention generally relates to a cleaning arrangement for use in an image forming apparatus, and more particularly, to an improvement of a cleaning device provided with a cleaning roller.
Conventionally, as a cleaning device provided with a rotatable cleaning roller pressed against the surface of an image holding member for removal of toner remaining on said image holding member after transfer, there have been known two types of cleaning devices as referred to below.
(1) A cleaning device of a type arranged to cause the cleaning roller to rotate following rotation of the image holding member (disclosed, for example, in Japanese Patent Laid-Open Publication Tokkaisho No. 60-33582).
(2) Another type of a cleaning device adapted to forcibly drive the cleaning roller for rotation at a speed different from a moving speed of the surface of the image holding member (disclosed, for example, in Japanese Patent Laid-Open Publication Tokkaisho No. 61-34579).
In the known cleaning device of the above item (1), however, since friction force between the image holding member and the cleaning roller is small, residual toner fused and solidified, paper powder and loading material in the paper powder (talc, kaolin or the like), or products of corona discharge by a corona charger and transfer charger to be produced on the image holding member, etc. undesirably remain on the surface of said image holding member without being removed (Such remaining substances are generally referred to as residual toner, etc. hereinafter). Thus, as a series of image forming functions is repeatedly effected, residual toner, etc. remaining without being removed is accumulated on the surface of the image holding member, thus resulting in such a defect as soiling of images by the residual toner, etc.
On the other hand, in the conventional cleaning device of the above item (2), since the speed difference is imparted to the cleaning roller with respect to the image holding member which is being driven, the friction force between the image holding member and the cleaning roller may be increased, and therefore, the residual toner, etc. on the image holding member can be removed. However, due to the fact that the friction force also acts as resistance against rotation of the image holding member, irregular rotation of said image holding member tends to take place, thus adversely affecting the quality of images in some cases. More specifically, the resultant image is disturbed by slippage taking place in the exposure position or transfer position, or irregularity may take place in the density of the image to be formed through variation of time in which a developing device contributes to developing in a developing region.
In order to overcome the disadvantages as described above, there may be considered to form the surface of the cleaning roller by a material having a small friction coefficient so as to prevent the friction force between the image holding member and the cleaning roller from increasing. However, in this case, it is difficult to select a material which is capable of achieving a sufficient cleaning characteristic, and can simultaneously provide a friction force which will not give resistance to rotation of the image holding member.